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Drag measurements are made on each of the members of 2, 3 & 4-vehicle platoons. One-eighth scale vehicle models are used in a wind tunnel equipped with a suction surface ground plane for boundary layer control. Strong interaction between vehicles takes place for spacings less than one vehicle length, leading to drag values substantially lower than for an isolated vehicle. All vehicles in the platoon experience lower drag. The average drag coefficient for a 4-vehicle platoon at a nominal spacing of 0.2 vehicle lengths is just 56 percent of the drag of the vehicle in isolation. It is also concluded that little additional benefit is achieved by forming platoons longer than 6-7 vehicles. Finally, the 2-vehicle platoons are operated in different orientations-front-to-front, back-to-back and reversed-to provide an estimate for drag reduction sensitivity to vehicle shape.

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. In addition, greater use of newly developed computational tools holds promise for reducing the number of prototype tests, for cutting manufacturing costs, and for reducing overall time to market. Experimental verification and validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California. Companion computer simulations are being performed by Sandia National Laboratories, Lawrence Livermore National Laboratory, and California Institute of Technology using state-of- the-art techniques, with the intention of implementing more complex methods in the future.

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. Experimental validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California (USC). Companion computer simulations are being performed by Sandia National Laboratories (SNL), Lawrence Livermore National Laboratory (LLNL), and California Institute of Technology (Caltech) using state-of-the-art techniques.